Data from: Multi-electrode array for transcutaneous lumbar posterior-root stimulation

Interest in transcutaneous electrical stimulation of the lumbosacral spinal cord is increasing in human electrophysiological and clinical studies. The stimulation effects on lower limb muscles depend on the depolarization of segmentally organized posterior root afferents and, thus, the rostro-caudal stimulation site. In previous studies, selective stimulation was achieved by varying the positions of single self-adhesive electrodes over the thoracolumbar spine. Here, we developed a multi-electrode surface array consisting of 3 × 8 electrode pads and tested its stimulation-site specificity. The array was placed longitudinally over the spine covering the T10–L2 vertebrae. Two different hydrogel layer configurations were utilized: a single layer adhered to all electrode pads of the array and a configuration comprised of eight separate strips attached to the three transverse electrode pads of each level. Voltage measurements demonstrated that an effectively focused field distribution along the longitudinal extent of the array was not accomplished when using the single continuous hydrogel layer, and segmental selective stimulation of the posterior root afferents was not possible. The separate strips produced a focused electric field distribution at the rostro-caudal level of the electrode pads selected for stimulation. This configuration allowed for the preferential elicitation of posterior root-muscle reflexes in either the L2–L4 innervated quadriceps or the L5–S2 innervated triceps surae muscle groups. Such multi-electrode array for transcutaneous spinal cord stimulation shall allow for improved control of stimulation conditions in electrophysiological studies and time-dependent and site-specific stimulation patterns for neuromodulation applications.

在人体电生理学与临床研究领域，腰骶段脊髓经皮电刺激（transcutaneous electrical stimulation of the lumbosacral spinal cord）的关注度正持续提升。该刺激对下肢肌肉的作用效果，取决于节段性排布的后根传入纤维（posterior root afferents）的去极化过程，进而与刺激位点的头尾侧（rostro-caudal）位置密切相关。既往研究中，研究者通过在胸腰段脊柱表面调整单块自粘式电极（self-adhesive electrodes）的位置，实现了选择性刺激。本研究中，我们研发了一款包含3×8个电极垫的多电极表面阵列，并对其刺激位点特异性进行了验证。该阵列沿脊柱纵向放置，覆盖T10至L2椎骨。本研究采用两种不同的水凝胶层配置方案：其一为将单层水凝胶贴合至阵列的全部电极垫；其二为8条独立水凝胶条带的配置方案，每条条带分别附着于对应节段的3个横向（transverse）排布的电极垫。电压测量结果显示，若使用连续单层水凝胶，无法在阵列的纵向范围内形成有效的聚焦电场分布，因此无法实现后根传入纤维的节段性选择性刺激。而独立条带配置则可在选定刺激的电极垫对应的头尾侧节段形成聚焦电场分布。该配置可优先在L2-L4神经支配的股四头肌，或是L5-S2神经支配的腓肠肌群中诱发出后根-肌肉反射（posterior root-muscle reflex）。这款用于腰骶段脊髓经皮电刺激的多电极阵列，有望在电生理学研究中实现对刺激条件的更精准调控，并可为神经调控（neuromodulation）应用提供时程依赖且位点特异性的刺激模式。